Project 2 in the Craniofacial Anomalies Research Center has as its primary goal the characterization of human genes that play a role in developmental defects of facial structures. The project provides a bridge between the epidemiology and clinical studies carried out in Project 1, the development of candidate genes that occurs in Project 3 and the resource for using animal models for more detailed characterization of human genes in Project 4. Project 2 relies heavily on the strategies and techniques of positional cloning and includes four specific aims. First will be an expanded effort at the positional cloning at the gene causing Van der Woude syndrome, a dominantly inherited form of cleft lip and palate. It will use a high resolution genetic and recombinant map and a patient recently identified with a microdeletion of a tightly linked microsatellite marker. Second will be continued efforts at identifying the gene involved in Rieger syndrome (which includes craniofacial abnormalities and cleft palate), relying on both a narrow linkage localization with the initiation of a YAC contig and by making use of two balanced translocation patients with the Rieger phenotype that map to the targeted area and likely disrupt the etiologic gene. Third, efforts will continue at high resolution linkage mapping and gene characterization of the Borjesson-Forsman-Lehman and dentinogenesis imperfecta syndromes. For both of these disorders, our efforts focus around continuing to develop linkage-based resources while detailed gene searching protocols are being carried out in collaboration with Drs. David Schlessinger at Washington University and Michael Dixon at the University of Manchester. Finally, a search will be carried out for non-Mendelian inheritance secondary to microdeletions or isodisomy in nuclear families of children with either syndromic or non syndromic forms of cleft lip and palate. This component is made practical by the availability of high throughout genotyping using robotics. The search will use both candidate genes identified through Projects 1, 3 and 4 and high heterozygosity short tandem repeat polymorphisms that are densely mapped across the human genome. Project 2 will discover new genes involved in human craniofacial development and allow more detailed genetic, molecular, developmental and environmental characterizations of how genes act and interact with one another.